In a process of fabricating a superjunction power device, a process using selective epitaxial growth which is advantageous in terms of cost has increased in recent years.
A planarizing process is required in a process of forming a deep trench, a process of forming an epitaxial layer in the deep trench by using the selective epitaxial growth, a process of forming an MOSFET structure on the epitaxial layer, and the like.
Further, in a postprocess, an alignment mark is used for accurate alignment during layer to layer matching; however, the alignment mark may be damaged by the planarizing process. Therefore, a technology of fabricating a semiconductor device is required so as to prevent the alignment mark from being damaged during the planarizing process.